Instrumentation and Communications Subsystem
This subsystem provides the communications loop between the Telescope and the Tracking and Data Relay Satellites TDRS , receiving commands and sending data through the HGAs and LGAs. All information passes through the Data Management Subsystem DMS . S-Band Single Access Transmitter SSAT . HST is equipped with two SSATs. S-band identifies the frequency at which the science data is transmitted and single access specifies the type of antenna on the TDRS satellite to which the data is sent. is a...
Hst Operations
Hubble Space Telescope operations comprise 1 science operations and 2 mission operations. Science operations plan and conduct the HST science program observing celestial objects and gathering data. Mission operations command and control HST to implement the observation schedule and maintain the Telescope's overall performance. These two types of operations often coincide and interact. For example, a science instrument may observe a star and calibrate incoming wavelengths against standards...
Electrical Power Subsystem
Power for the Telescope and science instruments comes from the Electrical Power Subsystem EPS . The major components are two SA wings and their electronics, six batteries, six Charge Current Controllers CCC , one Power Control Unit PCU and four Power Distribution Units PDU . All except the SAs are located in the bays around the SSM Equipment Section. During the servicing mission, the Shuttle will provide the electrical power. After deployment, the SAs will begin converting solar radiation into...
Physical Description
ACS will reside in an axial bay behind the HST main mirror. It is designed to provide HST with a deep, wide-field survey capability. The primary design goal of the ACS WFC is to achieve a factor of 10 improvement in discovery efficiency compared to WFPC2. Discovery efficiency is defined as the product of imaging area and instrument throughput. Grism spectroscopy low resolution R 100 wide-field spectroscopy from 5500 to 11,000 A, available in both the WFC and the HRC. Objective prism...
OTA Equipment Section
The OTA Equipment Section is a large semicircular set of compartments mounted outside the spacecraft on the forward shell of the SSM see Fig. 5-25 . It contains the OTA Electrical Power and Thermal Control Electronics EP TCE System, Fine Guidance Electronics FGE , Actuator Control Electronics ACE , Optical Control Electronics OCE and the fourth DMS DIU. The OTA Equipment Section has nine bays seven for equipment storage and two for support. All bays have outward-opening doors for easy astronaut...
Data Management Subsystem
The DMS receives communications commands from the STOCC and data from the SSM systems, OTA and science instruments. It processes, stores and sends the information as requested see Fig. 5-10 . 3. Scientific data from the SI C amp DH unit 4. Telescope engineering status data for telemetry 5. System outputs, such as clock signals and safemode signals. Advanced Computer. The Advanced Computer is a general-purpose digital computer for onboard engineering computations. It executes stored commands,...
Maneuvering Characteristics
The Telescope changes its orientation in space by rotating its reaction wheels, then slowing them. The momentum change caused by the reaction moves the spacecraft at a baseline rate of 0.22 degree per second or 90 degrees in 14 minutes. Figure 6-2 shows a roll-and-pitch maneuver. When the Telescope maneuvers, it takes a few minutes to lock onto a new target and accumu V1 Roll Maneuver Viewing Away From Sun V1 Roll Maneuver Viewing Away From Sun V2 Pitch Maneuvers Maneuver plane contains Sun V2...
Secondary Mirror Assembly
The Secondary Mirror Assembly cantilevers off the front face of the main ring and supports the secondary mirror at exactly the correct position in front of the primary mirror. This position must be accurate within 1 10,000 inch whenever the Telescope is operating. The assembly consists of the mirror subassembly, a light baffle and an outer graphite-epoxy metering truss support structure see Fig. 5-23 . The Secondary Mirror Assembly contains the mirror, mounted on three pairs of alignment...
Near Infrared Camera and MultiObject Spectrometer
NICMOS is a second-generation instrument installed on the HST during SM2 in 1997. Its cryogen was depleted in 1998. During SM3B astronauts will install the NICMOS Cooling System NCS , which uses a new technology called a Reverse Brayton-Cycle Cryocooler see Fig. 4-6 . This type of mechanical cooler allows longer operational lifetimes than current expendable cryogenic systems. The attempt to revive NICMOS with NCS is viewed as an experimental application of a promising new technology. There is...
Pointing Control Subsystem
A unique PCS maintains Telescope pointing stability and aligns the spacecraft to point to and remain locked on any target. The PCS is designed for pointing within 0.01 arcsec and holding the Telescope in that orientation with 0.007-arcsec stability for up to 24 hours while HST orbits the Earth at 17,500 mph. If the Telescope were in Los Angeles, it could hold a beam of light on a dime in San Francisco without the beam straying from the coin's diameter. Nominally, the PCS maintains the...
Orbital Replacement Unit Carrier
An ORUC is a pallet outfitted with shelves and or enclosures that is used to carry replacements into orbit and to return replaced units to Earth. For SM3B the Cblumbia payload bay will contain three ORUCs. All ORUs and scientific instruments are carried within protective enclosures to provide them a benign environment throughout the mission. The enclosures protect the instruments from contamination and maintain the temperature of the instruments or ORUs within tight limits. Instruments are...
Primary Mirror Assembly and Spherical Aberration
As the Telescope was first put through its paces on orbit in 1990, scientists discovered its primary mirror Fig. 5-17 Light path for the main Telescope Fig. 5-17 Light path for the main Telescope attenuate reflected light from unwanted bright sources, to the 94.5-inch 2.4-m primary mirror. Reflecting off the front surface of the concave mirror, the light bounces back up the tube to the 12-inch 0.3-m -diameter convex secondary mirror. The light is now reflected and converged through a 23.5-inch...
Structures and Mechanisms Subsystem
The outer structure of the SSM consists of stacked cylinders, with the aperture door on top and the aft bulkhead at the bottom. Fitting together are the light shield, the forward shell, the SSM Equipment Section and the aft shroud bulkhead all designed and built by Lockheed Martin Space Systems Company see Fig. 5-4 . Aperture Door. A door approximately 10 feet 3 m in diameter covers the opening to the Telescope's light shield. The door is made from honeycombed aluminum sheets. The outside is...
Support Systems Module
The SSM encloses the OTA and the science instruments like the dome of an Earth-based observatory. It also contains all of the structures, mechanisms, communications devices, electronics and electrical power subsystems needed to operate the Telescope. This module supports the light shield and an aperture door that, when opened, admits light. The shield connects to the forward shell on which the SAs and High Gain Antennas HGA are mounted. Electrical energy from the SAs charges the spacecraft...
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Special thanks to everyone who helped pull this book together. Pat Sharp - Text and graphics integration Computer generated 3-D illustrations provided by Tim Cole, Kevin Balch, David Green, Nick Dellwo Background information provided by Brian Woodworth, Donna Weaver, Ann Jenkins, Monty Boyd, Ray Villard, Dave Leckrone
Fine Guidance Sensor Filter Wheel
Each FGS has a filter wheel for astrometric measurement of stars with different brightness and to classify the stars being observed. The wheel has a clear filter for guide-star acquisition and faint-star greater than 13 apparent visual magnitude astrometry. A neutral-density filter is used for observation of nearby bright stars. Two colored filters are used to estimate a target's color chemical index, increasing contrast between close stars of different colors or reducing background light from...
Orbital Characteristics
The Telescope's orbit is approximately 320 nmi 593 km . The orbit inclines at a 28.5-degree angle from the equator because the Shuttle launch was due east from Kennedy Space Center. This orbit puts the Sun in the Telescope orbital plane so that sunlight falls more directly on the Solar Arrays. In addition, 320 nmi is high enough that aerodynamic drag from the faint atmosphere will not decay the Telescope's orbit to below the minimum operating altitude. HST completes one orbit every 97 minutes,...
Focal Plane Structure Assembly
The FPS is a large optical bench that physically supports the science instruments and FGSs and aligns them with the image focal plane of the Telescope. The -V3 side of the structure, away from the Sun in space, supports the FHSTs and RSUs see Fig. 5-24 . It also provides facilities for on-orbit replacement of any instruments and thermal isolation between instruments. The structure is 7 feet 2.1 m by 10 feet 3.04 m long and weighs more than 1200 pounds 545.5 kg . Because it must have extreme...
Processor
During Servicing Mission 3A SM3A , astronauts replaced Hubble's original main computer, a DF-224 coprocessor combina tion, with a completely new Advanced Computer based on the Intel 80486 microchip. This computer is 20 times faster and has six times as much memory as the one it replaced see Fig. 7-3 . In a good example of NASA's goal of faster, better, cheaper, commercially developed and commonly available equipment was used to build the new computer at a fraction of the cost of a computer...